So I was using this mod along with The Armory mod, and I believe one of the items it adds is a "Poisonous Small Heart" or something along those lines. Basically, if you run over it you pick it up and lose 10 health. I picked it up, died, and received the death screen. Death source was "". So I'm guessing there's some weird interaction with the two mods, but luckily it seems to be a pretty edge case scenario.